The Vasafan link towards the end of the thread shows some of the tests I have done with Vaclav's 55mm beastie, more than 800g of thrust, probably the best 55mm set up (best meaning highest thrust / best efficiency) if you put the right motor in, but at a cost, 4 motors, 4 EDFs around 400 euro.

Took my Vulcan out for her first full system test today. Did some fantastic fast taxi runs.

All my concerns about lack of power with my EDF choice vanished today!

Despite choosing some thick balsa, the total weight including a couple of 5000mAh 3S lipos came to just under 4.5Kg and she was off like a rocket. I had to fight to keep her on the ground (which was important as I live in the centre of London). Happily I managed to build up quite a crowd and a teacher from a local school had asked me to do a talk for the children and all the children watching want to build their own now!! Result!

The tests came to a natural end when I taxied it into a car, minor wing damage... Easily repairable

Going back to late 1990s 4.5kg (10lb) EDFs were being put into the air with 4 x 70mm fans on brushed motors with around 500g thrust per fan (for example the prototype for the B2 I am building) and they flew OK, nothing startling like unlimited vertical but they flew. As you can get that amount of thrust (and more) out of a 55mm fan now then the set up is fine as you have found.

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Going back to late 1990s 4.5kg (10lb) EDFs were being put into the air with 4 x 70mm fans on brushed motors with around 500g thrust per fan (for example the prototype for the B2 I am building) and they flew OK, nothing startling like unlimited vertical but they flew. As you can get that amount of thrust (and more) out of a 55mm fan now then the set up is fine as you have found.

The whole ducting set up I have in this model is sub optimal (intakes are a bit rough too), 2 kinks around the support boom... I expect to be able to get more thrust, now I have a better understanding of what I'm doing, I have figured out a way to support the wing without such a ridiculously large support boom.

Ok, breaking news... My girl friend has suggested we scale up for the next one... 8ft over the existing 6ft... I'm 100% behind her, but we simply don't have the space to build it that big

AND, love the go big or go home attitude. what's not to like? she's gonna get you in trouble once she sees that 20 footer and wants you to build one. LMAO.

Michelle does deserve a lot of credit for this model, she did most of the drawing, cutting and gluing... Not to mention nagging me when my motivation fell off a bit!

As this project came together we discussed just how large we might want to go for the next one, and the figure we homed in on was 37ft (about 11m) as the biggest we could realistically go with our 2 man time/resources/budget... But the limiting factor here is space... The smallest work area would probably need to be almost double that size, and we just can't afford that (England bing a bit smaller than Canada).

At that size, we are entering hombuild airplane teratory (see "A plane is born" with Mark Evans on YouTube to see what UK regulations are like)... Still something to aim for